Conductive nanocomposite hydrogels for flexible wearable sensors

In recent years, flexible wearable electronics have been widely used in smart wearable devices, micro-robots, and sensors due to their seamless integration with the human body and long-term monitoring capabilities. Hydrogels with good biocompatibility, versatility, and tunable mechanical properties compared to elastomers are becoming increasingly prominent in flexible electronics. Among them, conductive nanocomposite hydrogels have been extensively studied for their combination of multiple materials, resulting in higher elasticity, superior mechanical properties, and better physical/chemical/biological/electrical properties. Herein, we review the recent research advances in conductive nanocomposite hydrogels for sensor applications. First, we discuss the characteristics, design strategies, and applications of conductive nanocomposite hydrogels with different conductive compositions, including those based on carbon-based nanomaterials, polymer nanofillers, metal nanofillers, and the emerging 2D materials MXenes. Second, the properties of conductive nanocomposite hydrogels are described in detail, such as their mechanical properties, adhesion properties, self-healing properties, and anti-freezing properties. Finally, the design of future nanocomposite conducting hydrogel sensors is presented with their perspectives and challenges. We present a comprehensive review of the recent research advances in the field of sensors based on hydrogels with nanofillers. The characteristics and design strategies of nanofillers are highlighted and multiple properties of conductive nanocomposite hydrogels are described.